The present invention relates to fuel storage vaults and, in particular, to a ventilated, below-grade, multi-section cast concrete containment vault which contains one or more primary liquid storage tanks. A manhole permits access to the vault and spill and overflow containment assemblies direct spillage at included fill pipes to secondary or tertiary storage spaces. Dispensing pumps are secured to a cast cover containing sundry conduits, accessory fixtures and support equipment.
A byproduct of society""s increasing awareness to the environment and growing concerns toward ground water contamination and the adverse effects of spilled petrochemicals (e.g. oil, gasoline etc.) has been the institution of varieties of regulatory controls over related storage vessels. The controls are intended to promote safe fuel storage and contain spills. A primary goal is to avoid contaminated soils, such as are commonly found at the sites of gasoline stations, fueling depots and other fuel handling sites. The contamination can insidiously occur over time from small leaks or from a single large spill.
The fuel delivery industry has a separate desire for automatic, attendant free dispensing stations. The station should be compatible with all regulatory requirements and permit fuel delivery with either cash or credit card. Appurtenant storage tanks may either mount above or below grade and controls should be available to make the tanks substantially self-sufficient.
A variety of below-grade storage containers have been developed for containing pressurized and non-pressurized, flammable liquids, such as gasoline, propane or natural gas. Some of these containment vessels and tanks are shown at U.S. Pat. Nos. 1,958,487; 3,151,416; 3,995,472; 4,183,221; 4,607,522; and 4,653,312. The foregoing containers generally provide assemblies which include a primary metal containment chamber that is surrounded by a reinforcing material, such as concrete. Various arrangements of intervening layers of insulators and/or liquid impermeable materials are also included in the various tank assemblies.
Numerous above-grade storage vessels are also known. Most of these vessels provide only a tank assembly having a single skin or single layer of material, such as metal or concrete. Rupture or damage to the tank wall most typically results in an uncontrolled and uncontained spill. To avoid uncontained spills, some tanks are mounted behind a surrounding berm wall or dike.
In lieu of a dike, some tanks are constructed with a multi-layered construction that includes a primary tank surrounded by a concrete or metal structure. The primary tank may or may not be integrated into the surrounding structure. U.S. Pat. Nos. 2,083,491; 2,136,390; 2,777,295; and 4,513,550 disclose cast concrete containment chambers wherein the structural walls include liquid impermeable liners.
Still other above-grade storage vessels are disclosed at U.S. Pat. Nos. 2,544,828; 3,562,977; 4,366,654; 4,372,906; 4,552,166; 4,826,644; 4,911,326; 4,934,122; and 4,986,436. Various of the foregoing storage tanks provide a primary metal containment chamber which is surrounded by a monolithic cast concrete vault. One or more intervening membranes, impermeable to a contained liquid, are also provided to obtain secondary containment.
Another metal storage vessel having secondary containment is shown at U.S. Pat. No. 4,895,272. Also included in this tank is an assembly for directing spillage from the vent into a secondary storage space. U.S. Pat. No. 5,769,109 discloses a spill containment collar to direct spillage into the primary tank and/or a secondary storage space.
A principal deficiency above-grade storage containers is that the primary tank is exposed to a variety of physical dangers that can effect the life of the container. The sealed concrete tanks are also subject to potential cracking with thermal expansion and contraction; physical damage due to handling or collision from automobiles, trucks, on-site equipment or the like; and potential corrosion of reinforcement members within the concrete, such as from condensation which can form between the steel liner and surrounding concrete assembly. Damage to any one of the container components can require replacement of the entire assembly.
In preference to a monolithic assembly, a modular assembly permits selective replacement of one or more of the container components in the event of damage or normal wear and tear to the individual components. A modular construction is also more accommodating of conventional pre-cast manufacturing processes, such as are used to form open top septic tanks and detachable covers.
The containment tank of the present invention was developed to accommodate all enacted regulations, especially applications requiring storage of gasoline. A further purpose was to accommodate concerns of the user to cost and repair or replacement of portions of the containment system and to provide a system that lends itself to an attendant free, fuel dispensing station. The tank is constructed in the form of a pre-cast concrete housing which surrounds one or more internal storage tanks. The housing includes a base and cover and is constructed to accommodate burial and support one or more fuel dispensers directly to the cover. Manhole access and spill and rupture containment provisions are also provided.
It accordingly is a primary object of the invention to provide an environmentally friendly liquid containment vessel that can be mounted above or below-grade.
It is a further object of the invention to provide a vessel including a reinforced cast concrete base and a detachable cast concrete cover.
It is a further object of the invention to provide a vessel including one or more primary liquid storage tanks that are secured to the cover and provide secondary and/or tertiary containment space to collect spills.
It is a further object of the invention to provide a cover having a manhole access port and a ventilated base sized to permit internal examination for leakage at the primary tanks.
It is a further object of the invention to provide a cast concrete base that supports one or more primary storage tanks and wherein the cover includes sundry conduits, fixtures and accessories to support one or more dispensing pumps mounted to the cover.
It is a further object of the invention to provide a sump and one or more siphon assemblies that communicate with the interior space of the base to facilitate removal of condensation and the recovery of leaked or spilled liquids.
It is a further object of the invention to provide a raised spill containment collar, that surrounds fill, dispensing and or vent pipes that open to the primary storage tanks, to collect and direct any spillage to the primary tank, secondary storage space within the base or to an auxiliary or tertiary storage tank.
Various of the foregoing objects, advantages and distinctions of the invention are obtained in a presently preferred construction which provides an open-topped, reinforced cast concrete base and a separately cast, detachable cover. The cover includes a number of permanently mounted conduits and junction boxes and support platforms for one or more dispensing pumps. A manhole access port is separately provided which opens to the interior of the base. The cover is cast to support the weight of covering earth and vehicles which may pass over the cover.
Each dispenser support platform defines a spill containment collar which surrounds fill, dispensing and/or vent standpipes to collect spillage that may occur during filling or with liquid expansion. Conduits direct collected spillage to the secondary containment space within the base or to an auxiliary collection tank. Other standpipes permit monitoring the stored liquid and inspection of the secondary and tertiary containment spaces. The various standpipes can be incorporated into guard stanchions mounted about the dispensing pumps.
The base supports one or more primary liquid storage tanks, which are formed of steel or fiberglass. The base and cover may be lined with a thermal insulator. A sump region at a low point of the base and a siphon assembly are provided. The siphon assembly removes condensation, leakage or spillage. A liquid and vapor tight seal mounts between the base and cover. Separate resilient seals are cast into the cover or fitted to surround the various standpipes.
Air ventilation equipment and/or supply and exhaust ports are provided in the base and cover as necessary to facilitate internal inspection, maintenance and spill collection. Fans circulate and discharge air from the base during inspection.
Still other objects, advantages and distinctions of the invention will become more apparent upon reference to the following detailed description with respect to the appended drawings. Similar components and assemblies shown at the various drawings are referred to with similar alphanumeric reference characters. To the extent various modifications and improvements have been considered, they are described as appropriate.